Not to drag this out any more, because fair enough if you feel that way. But when it comes out on DVD, give it one or two more viewings. Because I felt that the characters could have had more to do on first impression too. I'm beginning to sound like a broken record now, but that was also my first impression of Blade Runner. Yeah, Deckard and Rachel and Pris and Batty are nicely done, but honestly who the hell are any of the other characters? All good actors, but basically nothing there. But the more you re-watch, the more subtleties you pick up, and by the third or fourth viewing you find yourself actually enjoying Edward James Olmos, who--in my memory--comes across as a paper-thin glorified extra on first impression. But side characters like Chew and Gaff, you begin to understand them as characters, and Ridley Scott knew this because he lived with the film, but he made the mistake of forgetting that you only begin to see them in three-dimensions when you have seen the film as much as he had. That's why Blade Runner can sometimes make a bad first impression but become a major genre classic on repeat viewings. I had that experience myself, and I saw it in the 1990s too.
And I feel very, very similarly about Prometheus. Weyland, Fiefeld, minor characters like that, there actually is a lot more to them than may first seem, and characters like Vickers and Janeck are IMO possibly the best characters in the film but they do require more than one viewing to fully appreciate all that went into them. When you really start breaking it down, a lot of the "stupid" things in the film aren't as stupid as people say, but I can see why it may seem that way on first impression.
I realize this sounds like an excuse--just watch the film enough times and you'll begin to ignore the problems--but I don't believe it is any more than it is for Blade Runner. The characters in Prometheus are not as eye catching and memorable as Alien and Aliens, but I would put them on par with something like Blade Runner and Alien 3. Like those films, they may seem thin at first, especially since the visuals are so overwhelming, but there is a lot more going on than one viewing would reveal. So my advice, if you like the Alien franchise, is give the film a second or third viewing and just soak in all the details, because it's the details where Prometheus really shines.